DK2223984T3

DK2223984T3 - Press-on twist-off container closures

Info

Publication number: DK2223984T3
Application number: DK10006004.5T
Authority: DK
Inventors: Christiane Poel-Asendorf; Rüdiger Wittenberg; Georg Schlenk
Original assignee: Actega Ds Gmbh
Priority date: 2007-11-09
Filing date: 2008-11-07
Publication date: 2018-12-03
Also published as: TR201802903T4; EP2562095A3; PL2223984T3; EP2562095A2; EP2209722B1; HUE045874T2; EP2562095B1; EP2918652A1; PL2562095T3; DE202008018549U1; LT3293241T; US20150061184A1; US8916078B2; WO2009059788A1; EP2058379A1; SI3293241T1; ES2661763T3; CN102123919B; CN103287692A; ES2661841T3

Description

DESCRIPTION

The invention relates to a press-on twist-off® vessel closure for vessels with an opening which is to be closed by the vessel closure and with an internal diameter of more than 2 cm, comprising a sealing element based on polymers which is disposed in the vessel closure in a manner such that it sealingly abuts the opening of the vessel in the closed condition.

Although the industry has been using PVC-free blends for the sealing liners of crown caps or screw-type bottle caps for some time, PVC-containing blends are still used for screw caps, lug caps, PT-caps and the like which act as vessel closures for vessels with a larger internal diameter of the opening. Usually, such PVC-containing blends are applied at room temperature in their liquid form by means of systems containing plasticizers.

However, the use of PVC-containing blends is not desirable. During conventional household waste incineration, halogenated polymers form acidic gases the escape of which into the atmosphere is harmful. Moreover, such PVC-based sealing elements require the use of plasticizers which are also considered to be a health risk.

Thus, there is a need for vessel closures which comprise a polymer-based but not a PVC-based sealing element which are suitable for vessels with relatively large openings with an internal diameter of more than 2 cm.

In a principal aspect, the invention provides a press-on twist-off® vessel closure which comprises a polymer-based sealing element which does not contain any PVC.

In general, in accordance with the invention, press-on twist-off® vessel closures are provided for such vessels the opening which is to be closed by the vessel closure having an internal diameter of more than 2 cm. This corresponds to an internal diameter which is larger than that of conventional beverage bottles closed in the familiar manner with crown caps, screw caps and the like as described, for example in EP 0 503 124 Bl.

The invention is of particular application to the production of relatively large - Z - vessel closures, i.e. for vessel openings with an internal diameter of more than 2.5 cm up to those where the internal diameter of the opening to be closed is greater than 4 cm. US 6 235 822 describes vessel closures with a sealing element which does not contain any PVC and which contains ethylene/octene copolymers as well as ethylene/acrylic acid copolymers. PT caps are not described. The Shore A hardness of the blend is not given, and nor is the compression set (CS). WO 96/20878 describes vessel closures of the same type as in US 6 235 822. Here again, no information is provided regarding the Shore A hardness and CS of the blend. WO 95/05427 discloses vessel closures with a PVC-free sealing element based on LLDPE, with no information being provided regarding the Shore A hardness and CS. PT caps are not mentioned. DE-OS 1782 737 discloses vessel closures with PVC-free sealing elements based on polypropylene and ethylene/vinyl acetate copolymers, with no information being provided regarding the Shore A hardness and the CS. Here again, PT caps are not mentioned. EP 0 503 124 discloses vessel closures with sealing elements which contain no PVC and are based on butyl rubber, HDPE and EVA. The hardness and CS are not provided. US 5 272 236 discloses films and fibres which contain ethylene/alkene copolymers, but it does not concern vessel closures.

It is known from US 2006/19991 that block copolymers of ethylene and octene can be used for seals, including seals for vessel closures. In this regard, PVC may be included with them. Very high oil contents are possible. The sealing elements of vessel closures are always foamed in that document; details regarding the CS of such sealing elements are not provided.

The vessel closures described in EP 0 503 124, which are typically intended for the bottling of beer, soft drinks, juice and the like into conventional narrow- - J - necked beverage bottles, may have to withstand the treatments described therein, such as pasteurization and hot-filling. However, these are thermally considerably less-demanding processes than sterilization. The temperatures used for pasteurization and hot-filling are below 100°C; typical sterilization conditions are 121°C or even 132°C. The polymer materials to be used in context of the invention are adapted to maintain their sealing action to the extent necessary, on the one hand during the pasteurization and hot-filling processes and on the other hand in the sterilization process.

In addition, not all blends of the kind described in EP 0 503 124 can easily be used for larger closures. Even though EP 0 503 124 indicates that the blends described therein are also suitable for screw caps and the like, this often only applies if the processing properties are varied accordingly - in particular, by adding extender oil in order to improve the flowability. This is not always desirable, for example with regard to the risk of migration of the components of the blend into foodstuffs containing fats. PVC-free materials lacking a plasticizer have to be applied in a thermally sufficiently softened form. Seals of this type cannot be produced by rotating the blank and injecting the material, as is the case with PVC plastisols. Instead, this requires extrusion and appropriate shaping, for example, in general, in accordance with the production method of the invention, an initial vessel closure blank formed from metal or plastic is used, the inside of which preferably has been initially pre-treated with a suitable primer. A TPE lacquer, for example the primer lacquer developed by the company Rhenania, is particularly suitable. The most preferred blends according to the invention adhere particularly well to this lacquer.

Alternatively, a suitable primer coating may be applied by lamination, lining or possibly also by co-extrusion.

The polymer material which is to form the seal is applied to the inside of the pre-treated blank in a thermally-induced flowable form. For this purpose, an extrusion wherein the sealing blend is supplied at a temperature in the range 100°C to 260°C is particularly suitable.

If the sealing liner is in the shape of a disk, the extrusion may be carried out into the centre of the blank's inner surface.

Subsequently, the disk-shaped sealing element is formed from the extruded, still flowable material by appropriate stamping (in analogy to the known SACMI process).

In a variation, the sealing element may be formed away from the closure or closure blank by stamping a suitable polymer material and subsequent insertion into the closure or blank. This method, using SACMI for small closures, is known as outshell-moulding.

Clearly, the method according to the invention has the additional advantage over the known plastisol method that the sealing liner is already fully finished by forming (stamping) and - in contrast to the plastisol injection - does not require subsequent oven-curing.

If the sealing element formed in this manner is disk-shaped, it is preferred that a sealing element thickness of approximately 0.1-0.2 mm is provided in the central region of the closure, where there is no sealing effect because it lies within the vessel mouth.

If the vessel closure is completely flat, this will mean that the sealing element will have a corresponding thickness in its sealing region as well.

If, however, the vessel closure has a depression ("channel") in the region corresponding to the mouth of the vessel to be closed, which is generally the case with closures having PVC-based plastisol seals, then the sealing element may possibly be thicker in this region. This may be advantageous because of the greater elasticity of a thicker sealing element. In such cases, the sealing element often has a preferred thickness of about 1 mm in its sealing region. A more complex shaping may also be provided in the region of the sealing element which sealingly contacts the vessel mouth; in particular, one or more sealing lips may be formed. This may be done by appropriate shaping when the extrudate is stamped. The sealing element may then have an accordingly greater thickness in the region of such sealing lips, for example of up to 3 mm.

The blends defined in claim 1 based on thermoplastic elastomers may be employed in order to carry out the invention.

The blend can be adapted to each specific purpose with regard to Shore hardness, modulus of elasticity, rheological properties and the like by means known from the prior art.

It is possible to provide the sealing liners according to the invention with barrier properties against oxygen and taste-affecting blends such as trichloroanisole by generally known procedures. Similarly and once more analogously to known procedures, the sealing elements according to the invention can be provided with the desired pressure maintenance or overpressure valve properties, respectively.

Advantageously, the vessel closures according to the invention are provided in a manner such that they exhibit a vacuum retention of the kind which is currently provided by conventional closures.

The desired vacuum retention is in general the extent to which an initially provided vacuum in the empty part of the closed vessel is maintained even after pasteurization or sterilization and after the expiry of the subsequent minimum shelf life of the product. As an example, it might be required that a closed glass jar containing food has an initial internal pressure of less than 0.2 bar and that the internal pressure must not exceed 0.2 bar up to the end of the minimum shelf life (minimum shelf life).

Typically, the vacuum retention is measured by perforating the cap of a random sample of vessels after pasteurization or sterilization, thus connecting the interior with a manometer. The internal pressure is read off and recorded. In another random sample, the progress of, for example the minimum shelf life can now be simulated by steam treatment at an elevated temperature ("accelerated ageing"). Afterwards, the resulting internal pressure is measured as in the first random sample. A comparison of the results shows whether the product satisfies the requirements. This is not the case if the admissible internal pressure is exceeded in too large a number of vessels in the random samples.

In particular, the present invention also relates to press-on twist-off® vessel closures formed from metal or plastic for vessels for receiving beverages or foodstuffs, having a sealing liner, the material thereof being selected such that the potentially harmful migration of material components into the beverage or foodstuff is prevented.

These requirements are especially relevant for baby food, which is typically sold in jars having a press-on twist-off®-closure.

This migration of components of the packaging (which may also encompass the sealing liner of the vessel closure) into the foodstuff is not only generally undesired, but also strictly regulated by legal requirements. Examples of such requirements are the EC directives 1935/2004, 2023/2006, 2002/72/EC and 372/2007.

The extent of the migration, if monitored, is determined by methods as specified in particular in DIN EN 1186. Such methods are also applied in the context of the present invention.

It is no trivial task to provide vessel closures of the kind considered herein with PVC-free sealing liners when these closures have to comply with the aforementioned regulations with regard to the possible migration of their chemical components.

For small vessel closures, sealing liners having a barrier effect against specific contaminants have already been used, for example those described in EP 0 503 124.

However, the requirements to be met by sealing materials for vessel closures for larger vessel opening internal diameters are more demanding. For such purposes, it is particularly important to combine a sufficient flowability of the polymer material during production of the sealing element with sufficient sealing properties in the closed state; this also encompasses the tightness required nowadays against gas ingress or escape, optionally combined with an overpressure valve effect preventing the vessel from bursting upon heating or upon the generation of overpressure in the vessel for other reasons. Moreover, and in particular for purposes typical for vessels with larger opening diameters (for example preserves), the sealing element must also be capable of being used under sterilization conditions.

The vessel closures described in EP 0 503 124, which are typically provided for the bottling of beer, soft drinks, juice and the like into conventional narrownecked beverage bottles, may have to withstand the treatments described therein, such as pasteurization and hot-filling, however, thermally, these are considerably less demanding processes than sterilization. The temperatures used for pasteurization and hot-filling are below 100°C; typical sterilizing conditions are 121°C or even 132°C. The polymer materials used according to the invention are adapted to be suitable for pasteurization or hot-filling on the one hand, and on the other hand to maintain their sealing action to the extent necessary at the higher sterilization temperatures.

Furthermore, the seals have to comply with the requirements indicated above with regard to the possible migration of chemical components.

The blends known in the art, however, often cannot be processed into larger sealing liners as this is prohibited by their flow properties.

In order to facilitate the processing of conventional blends, extenders and/or plasticizers are usually added to them. In particular, components are used which are liquid at the application temperature, such as extender oils (preferably white oil).

Surprisingly, it has now been shown that even though such blends are also processable into sealing liners with larger diameters - as the case may be after modifying the formulation - the vessel closures equipped with such sealing liners do not always comply with the legal requirements concerning the migration of chemical components.

It is a principal object of the invention to provide a suitable sealing liner for producing press-on twist-off® vessel closures with a suitable sealing liner which makes it possible to equip the vessel closure with a polymer-based sealing element that does not contain PVC and which complies with the legal requirements concerning the migration of components of packaging.

The invention solves this problem by means of the combination of features defined in claim 1.

In general, according to the invention, vessel closures are provided for such vessels wherein the opening to be closed by the vessel closure has an internal diameter of more than 2 cm. This corresponds to an internal diameter which is larger than that of conventional beverage bottles closed in the familiar manner with crown caps, screw caps and the like as described, for example in EP 0 503 124 Bl. The invention is particularly suitable for the production of relatively large vessel closures, i.e. for vessel openings with an internal diameter of more than 2.5 cm up to those where the internal diameter of the opening to be closed is greater than 4 cm.

More specifically, the present invention in general concerns press-on twist-off® closures, also known as PT caps, formed from metal or plastic, for vessels for receiving beverages or foodstuffs which have to be protected from the migration of packaging components as set out in the legal provisions. These are, for example, oil-containing or fat-containing foodstuffs, such as convenience food, but in particular oil-containing dressings and spice pastes, for example curry paste. The oil and fat components of such foodstuffs are particularly good solvents for extenders such as white oil, but also for plasticizer components.

In order to ensure a tight seal of the vessel, the vessel closures according to the invention comprise a sealing liner which meets the aforementioned requirements with regard to its processability, on the one hand and its sealing properties on the other hand, and which, moreover, complies with the legal requirements with regard to the migration of packaging components.

To this end, the material of the sealing liner is selected in a manner such that the migration of material components into the beverage or foodstuff is prevented.

The major component of the sealing liner material is a polymeric component as defined in claim 1 forming its principal structure. The properties of this primarily polymeric component can be suitably modified by adding further components, for example further polymers.

However, according to the invention, the sealing liner material only comprises very minor amounts of components which are fluid at the application temperature. Generally, the application temperature equals the ambient temperature, i.e. it is in the range of the usual ambient temperatures outdoors or in heated rooms, respectively.

Thus, in accordance with the invention, only minor or, preferably, no amounts of fluid extenders such as, in particular, white oil are added to the sealing liner material.

In preferred embodiments, the material comprises no more than 10%, preferably no more than 7%, in particular no more than 4%, and particularly preferably no more than 1% of such fluid components.

It is currently most preferred that, within the analytical detection limits at the application date, the material contains no components at all which are fluid at the application temperature.

Furthermore, preferably, the sealing liner material contains no plasticizers.

Since blends for such sealing liners are sometimes difficult to process without the addition of an extender when the material is composed, for example on the basis of styrene-containing block copolymers with elastomeric chain sections as described in EP 0 503 124, in particular if the diameter of the vessel closure exceeds 2 cm, materials which do not contain these polymers are preferred in the context of the present invention.

It is thus preferred that the material from which the sealing liner is formed contains neither the listed fluid extenders, nor plasticizers, nor styrene-containing block copolymers with elastomeric chain sections.

Instead, preferably, the polymer material, which is the major component of the sealing liner, is based on specific polyalkylenes which can be processed without extenders or the like, even to form sealing liners for vessel closures with diameters of more than 2 cm.

Thus, the invention concerns a copolymer comprising on the one hand polyethylene units and on the other hand being formed from an alkene monomer selected from propene, butene, hexene and (in particular) octene.

Such copolymers can be manufactured specifically with the desired physical properties using metallocene catalysts.

Preferably, said material has a Shore A hardness of 40-90, in particular a hardness of 60-75. The compression set determined in accordance with ASTM D 395 (70oC, 22h, 25% compression) is preferably in the range 30-70% and especially preferably in the range 30% to 50%.

Suitable polymers are described in EP 0 714 426. Therein, it is stated that these polymers as such are also processable into sealing elements, wherein no additives at all are to be used (p. 2, II. 26-28). The problem of material component migration is not addressed therein.

An example of a formulation comprises:

Ethylene-octene copolymer having the aforementioned properties: 45% EVA (14% VA): 40%

Highly flowable PP: 14%

Stabilizers (IRGANOX 1010, IRGAFOS 168): 0.2%

Lubricant (erucic acid amide): 0.2%

Lubricant (oleic acid amide): 0.2%

Pigment: 0.4%

According to these legal requirements, migration tests have to be carried out with the vessel closures according to the invention in the manner described in DIN EN 1186. This is the reason why these measurement methods are not reproduced in the context of the present application; said tests are herewith incorporated into the disclosure of the present application by reference to DIN EN 1186.

According to the invention, using the said polymer material allows the sealing liner produced thereby not only to be produced without a problem, but to possess the sealing properties described above. Moreover, such vessel closures are not only pasteurizable, but also sterilizable, and they comply with the previously described regulations of European law concerning the migration of polymer material components into the beverage or foodstuff contained in the vessel sealed in accordance with the invention.

In this respect, the requirements of said European legal directives, in particular in the context of the test criteria of DIN EN 1186, are suitable selection criteria for the polymer material which can be selected from the plurality of generally available blends by dispensing with components which are liquid at the application temperature and by dispensing with subsequent testing.

Claims

1. Press-on twist-off® metal or plastic container closure, for containers with an opening to be closed by the container closure, with an inner diameter of more than two cm, which container closure comprises a polymer-free PVC-based sealing element arranged in the container lid so that it seals abut against the opening of the container in the closed state, where a polymer compound is made sufficiently flowable by heating and is brought to the container lid in the area of the closure element to be formed and mechanically brought into the desired shape as the container after cooling; wherein the material of the closure element is selected so as to prevent migration of components of the material into the beverage or foodstuff, and wherein the material comprises at least one polymer component as the main component, which polymer component contributes to the sealing effect of the sealing element and the material is substantially free of components which are liquid by operating temperature, characterized in that the Shore A hardness of the polymer compound is between 40 and 90; that the polymer compound has a composition between 30% and 70%, determined in accordance with ASTM after 22 hours of storage at 70 ° C and a compression of 25%, and that the polymer compound comprises a copolymer comprising, on the one hand, polyethylene units and on the other is built from an olefin monomer selected from propylene, butene, hexene and especially octene.

2. Closed according to claim 1, characterized in that the polymer compound has a Shore A hardness of 60 to 75.

Closure according to claim 1 or 2, characterized in that the polymer compound does not comprise more than 10%, preferably not more than 7%, especially not more than 4% and especially not more than 1% of components which are liquid at operating temperature, especially white oil.

4. Closed according to claim 3, wherein the copolymer has been prepared from metallocene catalysts.

5. Closed according to any one of the preceding claims, characterized in that the polymer compound is designed so that the closure element can be inserted under pasteurization conditions (at up to 98 ° C).

6. Closed according to any one of the preceding claims, characterized in that the polymer compound is designed so that the closure element can be inserted under sterilization conditions (at 121 ° C, and preferably at 132 ° C).

7. A closure according to any one of the preceding claims, characterized in that the container closure provides a gas barrier function and / or a pressure relief valve function in the closed state.

8. Closed according to any one of the preceding claims, characterized in that the container lid exhibits vacuum retention in the closed state.

A closure according to any one of the preceding claims, wherein the polymeric material is provided as a granulate and is heated by an extruder.

Closure according to claim 1, characterized in that the container lid corresponds to an inner diameter of the container opening of more than 2.5 cm, preferably more than 3 cm, more preferably of at least 3.5 cm and more preferably of at least 4 cm.

A closure according to any one of claims 1 to 10, characterized in that the closure element can be inserted under pasteurization conditions (at up to 98 ° C) and the polymer compound comprises a copolymer comprising, on the one hand, polyethylene units and on the other built from an olefin monomer selected from propylene, butene, hexene and especially octene.

The closure of claim 11, wherein the copolymer has been prepared from metallocene catalysts.

The closure according to any one of the preceding claims, characterized in that the polymer compound is fed to the interior of a container closure precursor made of metal.